Context and Motivation: The intensification of global environmental concerns has necessitated the integration of sustainability principles into the operational frameworks of supply chain and logistics management. Outbound logistics—encompassing the distribution of finished goods to end consumers—represents one of the most carbon-intensive phases of supply chain activity, yet remains relatively underexplored in terms of monetized emission accountability. Purpose: This paper develops a conceptual framework for calculating and incorporating sustainability costs—specifically emission costs—into the cost of transport across different modes of freight movement. Drawing upon the Social Cost of Carbon (SCC) construct and relevant policy benchmarks, the study bridges a critical gap between emission quantification and its practical financial integration. Methodology: The study adopts a secondary data approach, synthesizing evidence from published academic literature, institutional reports, governmental policy documents, and international sustainability frameworks including the Global Logistics Emissions Council (GLEC) Framework and ISO 14083. Findings: A structured emission-cost model is proposed, wherein carbon emission intensities (g CO2e per tonne-kilometre) for five transport modes are monetized using a per-gram emission cost factor. The resulting per-trip emission cost differentials provide a transparent basis for sustainability-informed transport mode selection